Conventionally, fuel pumps are disclosed in JP-A-3-81596, JP-B2-2962828 (U.S. Pat. No. 5,328,325), JP-A-3-175196 (U.S. Pat. Nos. 5,697,152, 5,536,139 , 5,395,210), JP-A-6-229388 (U.S. Pat. No. 5,407,318), JP-A-7-217588. In the conventional fuel pump, multiple vane grooves are formed in a disc-shaped impeller along the rotative direction thereof. The vane grooves, which are adjacent to each other in the rotative direction, are partitioned with a partition wall. The impeller rotates to pressurize fuel in a pump passage formed along the vane grooves.
The impeller rotates, so that swirl-flow energy is generated in fluid. The swirl-flow energy is used for pressurizing fluid in the pump passage. When fluid flows from the pump passage into the radially inner side of the vane groove, swirl-flow energy of fluid decreases. As a result, a component of velocity of swirl flow along the rotation axis decreases, and the flow direction of fluid is approximated to the rotative direction. As described in JP-A-3-81596, U.S. Pat. No. 5,328,325, a partition wall, which is located on the rear side of a vane groove in the rotative direction, has a fore face on the fore side in the rotative direction, and the fore face is a flat face that is along the radial direction thereof. In this structure, the swirl flow does not pass through the grove vane along the fore face of the partition wall, and the swirl flow collides against the fore face of the partition wall in a large angle. The colliding force works in the direction opposite to the rotative direction of the impeller, and rotation of the impeller is disturbed.